Storage tube



w. SER1-HOLD ETAL 2,950,4G9

STORAGE TUBE Aug. 23, 1960 Filed March 25. 1958 ATTORNEY United StatesPatent O STORAGE TUBE Wolfgang Berthold, Belmar, NJ., and JrgenRottgardt,

Numberg, and Gerhard Heller, Ludwigsburg, Germany, assiguors toInternational Standard Electric Corporation, New York, N.Y., acorporation of Delaware Filed Mar. 25, 1958, Ser. No. 723,873 Claimspriority, application Germany Mar. 27, 1957 4 Claims. (Cl. 313-92) Forthe purpose of storing electric signals there are used cathode ray tubeswhich, depending on their respective iield of application, are equippedwith different kinds of fluorescent screens.

Image screens are known, consisting of phosphorescent luminoussubstances and in which the portions that are hit by an electron beamhave an afterglow effect which last for some time after the excitation.The reason for this resides in the fact that crystal electrons, whichare excited by the electron beam, are lifted into impurities of thecrystal, where they remain until being accidentally released from theimpurity by an energy quantum of the heat radiation and, under theemission of light, are forced to return to the original energy level.

The viewing of a phosphorescent image is only possible in the dark,because its light intensity is Very small.

Furthermore there are known image screens, substantially consisting ofan alkali-halide which, upon being bombarded by an electron beam,produces a tenebrescence phenomena, in the the portions hit by theelectron beam change their colour towards dark. Accordingly, in thiscase the image will only become visible when the screen is beingilluminated from the outside. The time of storage of these types ofimage screens is longer than with the phosphorescent types of imagescreens. By means of a new energy supply, e.g. by radiation with avisible light, or by heating the crystalline layer, the change in colourmay be eliminated again.

The article appearing in the Zeitschrift fr Naturforschung, 1955, pages620-630 by P. Dobrinski and H. Hinrichs describes the luminescence ofpotassium chloride activated with silver. It is discussed that NaCl-Agcrystals radiated by X-rays display the phenomenon of phosphorescence.

For many applications it is advantageous to provide a storage tube, witha screen image which is visible in the light as well as in the dark.Such screen properties are very useful e.g. for wide-range displays inthe directionndingand radar-technique. For example, when an observeronly uses the radar equipment as an auxiliary means, and when the directviewing or inspection of the surroundings during night-time requires apermanent or continuous dark-adaptation of the human eye, then everykind of illumination of the tube will act disturbingly. On the otherhand, during the day-time a bright image screen is by all meansdesirable. A tube combining both of these possibilities would render are-adaptation of the eye, which takes several minutes, or a superfluoustimewasting and circumstantial exchange of the tube.

The present invention provides a storage tube featuring both of theseadvantageous properties. The storage tube according to the invention isprovided with a screen on which the image recorded by an electron beamcontrasts with the screen within a bright surrounding bybeing amplied ona bright background, while appearing in the dark as a phosphorescentimage. Accordingly, the storage screen is not only featured by atenebrescence phenomena, but also, by phosphorescent phenomena. Thispossibility results from the discovery that an alkali-halide activatedwith particular metals exhibit uorescents when heated. As a luminoussubstance there are suitable alkali-halides, such as potassium chloride,which may be activated by traces of foreign substances, such asthallium, titanium, manganese, copper, uranium, lead or silver. Furtherit has proved to be very advantageous, to articially increase the numberof lattice defects, serving as the traps for the secondary electrons.This may be accomplished e.g. by an evaporation of the luminous layer ina micro-crystalline form, or else by way of ion bombardment.

Instead of activating the luminous substance there may `also be employeda double-layer screen, which is composed of corresponding substances.Thereby one of these layers displays tenebrescence, and the other onephosphorescence. A controlling of the desired screen property may beaccomplished by a corresponding arrangement of the screens and byvarying the accelerating voltage.

In the following the invention will be described in particular withreference to an exemplified embodiment shown in the accompanyingdrawing:

In this drawing the storage tube is shown in a sectional representation.The envelope is denoted by 1, and the gun system (or beam generatingsystem) is-denoted by 2. Reference numeral 3 designates a mica diskcarrying the screen substance 4. On the side of the mica disk not facingthe cathode there is arranged a transparent resistive layer or coating5, e.g. of S1102, and which, through the contacts 6 and 7, is connectedwith a source of voltage 8 controlled by switch 9, thus effecting aheating of the mica disk by a passage of current. On the side of themica disk facing the cathode there is evaporated the screen substance,which is activated with a corresponding foreign substance. Upon beinghit by the electron beam, the screen, within a bright surrounding, willdisplay a change in colour toward bluish-violet. If the screen is notilluminated from the outside then, upon heating of the mica disk, therewill appear the same image as a luminous phosphorescent picture.

While We have described above the principles of our invention inconnection with specific apparatus, it is to be clearly understood thatthis description is made only by way of example and not as a limitationto the scope of our invention as set forth in the objects thereof and inthe accompanying claims.

What is claimed is:

l. In a cathode ray tube comprising a screen and a source of energy, alayer of energy responsive material mounted on said screen whichexhibits the properties of phosphorescence in a first state andtenebrescence in a second state, and means for heating said layer toselectively change the state of said material to respond to said sourceof energy whereby said screen will either phosphoresce or tenebresce.

2. In a cathode ray tube the combination as in claim 1 wherein saidlayer consists of a mixture of fan alkali halide and a material from agroup consisting of thallium, titanium, manganese, copper, uranium, leador silver.

3. A cathode ray tube comprising a screen, a source of energy, `a layerof energy responsive material which exhibits the properties ofphosphorescence in a rst state and tenebrescence in a second stateapplied to one surface of said screen, a resistive layer applied to theother surface of said screen, means for applying `a source of voltage tosaid resistive layer so as to cause said energy responsive material tochange from said second state to said rst state.

4. A cathode ray tube comprising a mica disc, a

a t Y Y l 4j y l source of energy, a layer of energy responsive materialsaid tin oxide so as to cause said energy responsive macomprising amixture ofalkali halide and-a` material vfromV terial to change fromsaid second state to said first-state a group consisting of thallium,titanium, manganese, d he e of JLht t copper, uranium, lead or silver,which exhibits the proper- References Cite m t 1 1S pa en tiesy ofphosphoresceueein Ia rst statev andl tenebrescenceV UNITED STATESPATENTS ina-secondrstate applied to one smfaceofsaid mica disc,

Y 2,416,574 Fonda. Feb. 25, 1947 allayepof` tin oxide applied toY theother surface 0f said 2,435,435 Fonda Feb. 3, 1948 mica-disc, and meansfor applying asorce of Voltage to 2,447,851 Fonda Aug. 24, 1948

